Organic light emitting device

ABSTRACT

An organic light emitting device includes a first electrode formed over a substrate; an intermediate layer that is formed over the first electrode and includes an organic light emitting layer; a second electrode that includes a central electrode unit disposed in a central region and a peripheral electrode unit disposed in a peripheral region, the intermediate layer being disposed between the first and second electrodes; and a power unit configured to apply voltages to the first electrode and the second electrode. The power unit is configured to apply different voltages to the first electrode, the central electrode unit, and the peripheral electrode unit.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No.10-2011-0047462, filed on May 19, 2011, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Field

The present disclosure relates to/an organic light emitting device, andmore particularly, to an organic light emitting device that providesuniform brightness.

2. Description of the Related Art

An organic light emitting device generates a visible light from anorganic material disposed between two electrodes when a voltage isapplied to the electrodes. The organic light emitting device is anemissive device and has Various advantages.

Recent studies have been conducted using the organic light emittingdevices for illumination purposes besides using the devices inconventional display apparatus.

An organic light emitting device generates visible light havingrelatively uniform brightness when the organic light emitting devicehaving a small area is formed. However, when an organic light emittingdevice having a large area is formed, the brightness characteristic ofthe organic light emitting device differs from region to region.Therefore, there is a limit to securing a uniform brightnesscharacteristic of the organic light emitting device.

SUMMARY

One aspect of the present invention provides an organic light emittingdevice that can readily secure a uniform brightness characteristic.

According to an aspect of the present invention, there is provided anorganic light emitting device including: a first electrode formed over asubstrate; an intermediate layer that is formed over the first electrodeand comprises an organic light emitting layer; a second electrode thatcomprises a central electrode unit disposed in a central region and aperipheral electrode unit separated from the central electrode unit anddisposed in a peripheral region, wherein the intermediate layer isdisposed between the first and second electrodes; and a power unitconfigured to apply voltages to the first electrode and the secondelectrode, wherein the power unit is configured to apply differentvoltages to the first electrode, the central electrode unit, and theperipheral electrode unit.

The power unit may be configured to individually control the voltagesapplied to the central electrode unit and the peripheral electrode unitand further configured to apply different voltages to the centralelectrode unit and the peripheral electrode unit.

The power unit may apply the voltage to the peripheral electrode unitbefore applying the voltage to the central electrode unit.

The first electrode may be formed as a single body.

The first electrode may be connected to electrode voltage applicationunits and a voltage may be applied to edges of the first electrode.

The electrode voltage application units may be formed on the edges ofthe first electrode, respectively.

The power unit may be connected to the electrode voltage applicationunits and configured to apply the voltage to the first electrode.

Edges of the central electrode unit may have curved portions.

The center of the first electrode may coincide with the center of thecentral electrode unit.

The center of the central electrode unit may coincide with the center ofthe peripheral electrode unit.

The organic light emitting device may further include an electrodevoltage application unit formed to apply a voltage to the secondelectrode, wherein the first electrode comprises a recess portionrecessed from a side of the first electrode, and the recess portion isformed to overlap the electrode voltage application unit.

The second electrode further may include at least an additionalperipheral electrode unit separated from the peripheral unit, theperipheral electrode unit is disposed to surround the central electrodeunit, and the at least an additional peripheral electrode units isdisposed to surround the peripheral electrode unit disposed to surroundthe central electrode unit.

The power unit may be connected to the electrode units and configured toindividually apply voltages to the electrode units.

When a first one of the electrode units is disposed farther from thecenter of the second electrode than a second one of the electrode units,the voltage applied to the first electrode unit may be higher than thatapplied to the second electrode unit.

The power unit may be configured to differentially control periods oftime of application of the voltages to the electrode units.

The power unit may be configured to apply the voltage to the centralelectrode unit for a longer period of time than the peripheral electrodeunit.

When a first one of the electrode units is disposed closer to the centerof the second electrode than a second one of the electrode units, theperiod of time of application of the voltage to the first electrode unitis longer than that of the second electrode unit.

The centers of the electrode units may be formed to coincide with eachother.

Edges of at least some of the electrode units may have curved portions.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail embodiments thereofwith reference to the attached drawings in which:

FIG. 1 is a schematic plan view of an organic light emitting deviceaccording to an embodiment of the present invention;

FIG. 2 is a schematic plan view of a first electrode of the organiclight emitting device of FIG. 1, according to an embodiment of thepresent invention;

FIG. 3 is a schematic plan view of a second electrode of the organiclight emitting device of FIG. 1, according to an embodiment of thepresent invention;

FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 1;

FIGS. 5 and 6 are schematic drawings showing voltage differences inregions of the first and second electrodes when a voltage is applied tothe first and second electrodes of the organic light emitting device ofFIG. 1;

FIGS. 7 and 8 are graphs showing voltages applied to the first electrodeand the second electrode by using a power unit; and

FIG. 9 is a schematic plan view of an organic light emitting deviceaccording to another embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will now be described more fullywith reference to the accompanying drawings in which embodiments of theinvention are shown.

FIG. 1 is a schematic plan view of an organic light emitting device 100according to an embodiment of the present invention. FIG. 2 is aschematic plan view of a first electrode 110 of the organic lightemitting device 100 of FIG. 1, according to an embodiment of the presentinvention. FIG. 3 is a schematic plan view of a second electrode 120 ofthe organic light emitting device 100 of FIG. 1, according to anembodiment of the present invention. FIG. 4 is a cross-sectional viewtaken along the line IV-IV of FIG. 1.

Referring to FIGS. 1 through 4, the organic light emitting device 100includes a substrate 101, the first electrode 110, an intermediate layer140, the second electrode 120, and a power unit 160. The secondelectrode 120 includes a central electrode unit 121 and a peripheralelectrode unit 122.

Now, each of the members will be practically described.

The substrate 101 may be formed of a transparent glass material thatincludes SiO₂ as the main component. The substrate 101 according to thecurrent embodiment is not limited thereto, and may be formed of aplastic material. The plastic material that can be used to form thesubstrate 101 may be an organic material selected from the groupconsisting of polyethersulphone (PES), polyacrylate (PAR),polyetherimide (PEI), polyethyelenen napthalate (PEN),polyethyeleneterepthalate PET), polyphenylene sulfide (PPS),polyallylate, polyimide, poly carbonate (PC), cellulose triacetate(TAC), and cellulose acetate propionate (CAP).

The first electrode 110 is formed on the substrate 101. Although notshown, a buffer layer (not shown) may be formed between the substrate101 and the first electrode 110. The buffer layer provides a planarizedsurface on the substrate 101 and inhibits moisture and foreign materialsfrom penetrating into the substrate 101. The buffer layer may be formedof an insulating material.

The first electrode 110 is an anode electrode and may be formed ofvarious conductive materials. For example, the first electrode 110 mayinclude indium tin oxide (ITO).

For convenience of explanation, the first electrode 110 is morepractically depicted in FIG. 2. Referring to FIG. 2, the first electrode110 is not divided by a plurality of regions but is formed as one body.The first electrode 110 has a shape similar to a square. However, thepresent invention is not limited thereto, and the first electrode 110may have a polygonal shape such as a triangular shape, a pentagonalshape, or a circular shape. The first electrode 110 includes a grooveshaped recessed portion 110 a on a surface thereof. That is, therecessed portion 110 a is a region where a voltage is not applied whenthe voltage is applied to the first electrode 110, and thus, a visiblelight is not generated from the intermediate layer 140 corresponding tothe recessed portion 110 a.

A first electrode voltage application structure includes at least anelectrode voltage application unit 111 which is connected to the powerunit 160 and is formed in the first electrode 110 to apply a voltage tothe first electrode 110. The first electrode voltage application unit111 and the power unit 160 are electrically connected to each other viaelectric wires. Four electrode voltage application units 111 may beformed in side edges of the first electrode 110 as shown in FIG. 1.Although one of the electrode voltage application units 111 and a firstterminal unit 165 are illustrated to be connected to each other in FIG.1, each of the four electrode voltage application units 111 is connectedto the first terminal unit 165 of the power unit 160 via an electricwire. An identical voltage is applied to the four electrode voltageapplication units 111 by using the power unit 160. The number of theelectrode voltage application units 111 is not limited to four, and maybe one or more. The electrode voltage application unit 111 is connectedto the first terminal unit 165 such that a common voltage is appliedthereto.

When a voltage is applied to the first electrode 110, a relatively lowvoltage may be applied to the center P of the first electrode 110 due toa voltage drop (IR drop) because the center P is the farthest point fromthe electrode voltage application units 111. That is, since the voltageis applied from the sides of the first electrode 110 that is formed as asingle body having a large area, a voltage which is relatively lowerthan that applied to regions adjacent to the electrode voltageapplication units 111 is applied to the center P located remotely fromthe sides.

In particular, when the first electrode 110 is formed of a materialhaving a low electrical conductivity like ITO, the voltage drop mayfurther occur, and thus, a voltage that is applied to the center P maybe apparently lower than that applied to the side regions adjacent tothe electrode voltage application units 111.

The intermediate layer 140 is formed on the first electrode 110. Theintermediate layer 140 includes an organic light emitting layer (notshown) that emits visible light when a voltage is applied through thefirst and second electrodes 110 and 120. The intermediate layer 140 mayfacilitate the transmission of charges, and for the effective generationof visible light, may include at least one layer selected from the groupconsisting of a hole injection layer (HIL), a hole transport layer(HTL), an electron transport layer (ETL), and an electron injectionlayer (EIL) or a plurality of layers.

The second electrode 120 is formed on the intermediate layer 140. Forconvenience of explanation, the second electrode 120 is more practicallydepicted in FIG. 3. A second electrode voltage application structure 130is connected to the second electrode 120 to apply a voltage to thesecond electrode 120.

The second electrode 120 includes the central electrode unit 121 and theperipheral electrode unit 122. The peripheral electrode unit 122includes a first peripheral electrode unit 123, a second peripheralelectrode unit 124, and a third peripheral electrode unit 125. However,the present invention is not limited thereto, and, the peripheralelectrode unit 122 may be one or more than three.

The second electrode voltage application structure 130 includes acentral electrode unit voltage application unit 131, a first peripheralelectrode voltage application unit 133, a second peripheral electrodevoltage application unit 134, and a third peripheral electrode voltageapplication unit 135.

The central electrode unit 121 is disposed in the center of the secondelectrode 120. The center P of the second electrode 120 coincides withthe center P of the central electrode unit 121. The center P of thesecond electrode 120 and the center P of the first electrode 110 are thesame point.

In order to apply a voltage to the central electrode unit 121, thecentral electrode unit voltage application unit 131 extends to reach alower side of the central electrode unit 121 and is connected to thecentral electrode unit 121. The central electrode unit voltageapplication unit 131 is connected to the power unit 160.

More specifically, the power unit 160 may include a second terminalstructure 167 connected to the second electrode voltage applicationstructure 130. The second terminal structure 167 may include a pluralityof connection terminal units 161, 162, 163, and 164 for a one-to-oneconnection with the second electrode 120. In other words, according tothe present embodiment, the second electrode 120 includes the centralelectrode unit 121 and the peripheral electrode unit 122 that includesthe first peripheral electrode unit 123, the second peripheral electrodeunit 124, and the third peripheral electrode unit 125. Thus, the secondterminal structure 167 may include the central connection terminal unit161 connected to the central electrode unit 121, and a peripheralconnection terminal unit 166 connected to the peripheral electrode unit122. The central electrode unit voltage application unit 131 isconnected to the central connection terminal unit 161 of the power unit160 such that the voltage is applied to the first electrode unit 121 byusing the power unit 160.

The first peripheral electrode unit 123 is disposed peripherally to thecentral electrode unit 121 to surround the central electrode unit 121.Also, the first peripheral electrode unit 123 is separated from thecentral electrode unit 121 and the central electrode unit voltageapplication unit 131.

In order to apply a voltage to the first peripheral electrode unit 123,the first peripheral electrode voltage application unit 133 extends toreach a lower side of the first peripheral electrode unit 123 and isconnected to the first peripheral electrode unit 123. The firstperipheral electrode voltage application unit 133 is electricallyconnected to the first peripheral electrode connection terminal unit 162of the power unit 160. The first peripheral electrode voltageapplication unit 133 is separated from the central electrode unitvoltage application unit 131.

Also, the center P of the first peripheral electrode unit 123 coincideswith the center P of the central electrode unit 121.

The second peripheral electrode unit 124 is disposed peripherally to thefirst peripheral electrode unit 123 to surround the first peripheralelectrode unit 123. The second peripheral electrode unit 124 isseparated from the first peripheral electrode unit 123 and the firstperipheral electrode voltage application unit 133. Of course, the secondperipheral electrode unit 124 is separated from the central electrodeunit 121 and the central electrode unit voltage application unit 131.

In order to apply a voltage to the second peripheral electrode unit 124,the second peripheral electrode voltage application unit 134 extends toreach a lower side of the second peripheral electrode unit 124 and isconnected to the second peripheral electrode unit 124. The secondperipheral electrode voltage application unit 134 is electricallyconnected to the second peripheral electrode connection terminal unit163 of the power unit 160. The second peripheral electrode voltageapplication unit 134 is separated from the central electrode unitvoltage application unit 131 and the first peripheral electrode voltageapplication unit 133.

The center P of the second peripheral electrode unit 124 coincides withthe center P of the central electrode unit 121.

The third peripheral electrode unit 125 is disposed peripherally to thesecond peripheral electrode unit 124 to surround the second peripheralelectrode unit 124. The third peripheral electrode unit 125 is separatedfrom the second peripheral electrode unit 124 and the second peripheralelectrode voltage application unit 134. Of course, the third peripheralelectrode unit 125 is separated from the central electrode unit 121, thecentral electrode unit voltage application unit 131, the firstperipheral electrode unit 123, and the first peripheral electrodevoltage application unit 133.

In order to apply a voltage to the third peripheral electrode unit 125,the third peripheral electrode voltage application unit 135 extends toreach a lower side of the third peripheral electrode unit 125 and isconnected to the third peripheral electrode unit 125. The thirdperipheral electrode voltage application unit 135 is electricallyconnected to the third peripheral electrode connection terminal unit 164of the power unit 160. The third peripheral electrode voltageapplication unit 135 is separated from the central electrode unitvoltage application unit 131, the first peripheral electrode voltageapplication unit 133, and the second peripheral electrode voltageapplication unit 134.

Also, the center P of the third peripheral electrode unit 125 coincideswith the center P of the central electrode unit 121.

Through the above configuration, the power unit 160 may individuallycontrol voltages applied to the central electrode unit 121, the firstperipheral electrode unit 123, the second peripheral electrode unit 124,and the third peripheral electrode unit 125. Also, voltages differentfrom each other may be applied to the central electrode unit 121, thefirst peripheral electrode unit 123, the second peripheral electrodeunit 124, and the third peripheral electrode unit 125. For example, thepower unit 160 may sequentially apply increasing voltages to the centralelectrode unit 121, the first peripheral electrode unit 123, the secondperipheral electrode unit 124, and the third peripheral electrode unit125, which will be described later.

As described above, the first electrode 110 has the recessed portion 110a. The recessed portion 110 a is formed to correspond to the centralelectrode unit voltage application unit 131, the first peripheralelectrode voltage application unit 133, the second peripheral electrodevoltage application unit 134, and the third peripheral electrode voltageapplication unit 135. That is, the recessed portion 110 a is formed tocorrespond to the second electrode voltage application structure 130that applies a voltage to the second electrode 120.

A sealing member 150 protects the first electrode 110, the intermediatelayer 140, and the second electrode 120 from external moisture oroxygen. The sealing member 150 may be formed of various materials, andmore practically, may be formed of a glass material or a plasticmaterial. Also, even though the sealing member 150 is depicted tocontact the second electrode 120, the sealing member 150 may beseparated from the second electrode 120.

FIGS. 5 and 6 are schematic drawings showing voltage differences inregions of the first and second electrodes 110 and 120 when a voltage isapplied to the first and second electrodes 110 and 120 of the organiclight emitting device 100 of FIG. 1.

That is, FIGS. 5 and 6 show an operation of the organic light emittingdevice 100 to generate a visible light from the intermediate layer 140by applying voltages to the first electrode 110 and the second electrode120.

Referring to the drawing on the top side in FIG. 5, voltages applied toeach of the regions are depicted. More specifically, the power unit 160applies voltages V1, V2, V3, and V4, respectively, to the centralelectrode unit 121, the first peripheral electrode unit 123, the secondperipheral electrode unit 124, and the third peripheral electrode unit125. At this point, values of the V1, V2, V3, and V4 are V4>V3>V2>V1.The central electrode unit voltage application unit 131 is connected tothe central connection terminal unit 161, the first peripheral electrodevoltage application unit 133 is connected to the first peripheralelectrode connection terminal unit 162, the second peripheral electrodevoltage application unit 134 is connected to the second peripheralelectrode connection terminal unit 163, and the third peripheralelectrode voltage application unit 135 is connected to the thirdperipheral electrode connection terminal unit 164 so that the power unit160 applies different voltages to the regions 121, 123, 124, and 125 ofthe second electrode 120.

Referring to the drawing on the bottom side in FIG. 5, voltages appliedto each of the regions are depicted. More specifically, voltages VA, VB,VC, and VD are respectively applied to the central region of the firstelectrode 110, that is, a region corresponding to the central electrodeunit 121 of the second electrode 120, a region of the first electrode110 that corresponds to the first peripheral electrode unit 123, aregion of the first electrode 110 that corresponds to the secondperipheral electrode unit 124, and a region of the first electrode 110that corresponds to the third peripheral electrode unit 125.

As described above, since the first electrode 110 is formed as one body,basically a uniform voltage may be applied to the entire region of thefirst electrode 110 when a voltage is applied to the first electrode110. This is particularly important since the electrode voltageapplication units 111 are disposed on edges of the first electrode 110.However, in practice, since the area of the first electrode 110 is toolarge, a voltage drop (IR drop) occurs. Specifically, when a firstportion of the first electrode is disposed farther from the electrodevoltage application units 111 of the first electrode 110 than a secondportion of the first electrode, the voltage drop at the first portion isgreater than that at the second portion, and thus, the value of voltageat the first portion is smaller than that at the second portion.

As a result, although a uniform voltage is applied to the electrodevoltage application units 111 through a single power source, the levelsof the voltages being applied to each of the regions of the firstelectrode 110 may vary, that is, the values of the voltages are in theorder of VD>VC>VB>VA. At this point, since the first electrode 110includes ITO having a relatively high resistance instead of a metalhaving a relatively low resistance, the voltage drop in each of theregions of the first electrode 110 may more severely occur, andaccordingly, the voltage difference between VA and VD may be apparentlyincreased.

FIG. 6 shows voltage differences between regions of the first electrode110 and regions of the second electrode 120 corresponding to the regionsof the first electrode 110.

More specifically, a voltage difference between a voltage V1 applied tothe central electrode unit 121 of the second electrode 120 and a voltageVA applied to a region of the first electrode 110 corresponding to thecentral electrode unit 121 of the second electrode 120 is defined asΔVIA; a voltage difference between a voltage V2 applied to the firstperipheral electrode unit 123 of the second electrode 120 and a voltageVB applied to a region of the first electrode 110 corresponding to thefirst peripheral electrode unit 123 of the second electrode 120 isdefined as ΔV2B; a voltage difference between a voltage V3 applied tothe second peripheral electrode unit 124 of the second electrode 120 anda voltage VC applied to a region of the first electrode 110corresponding to the second peripheral electrode unit 124 of the secondelectrode 120 is defined as ΔV3C; and a voltage difference between avoltage V4 applied to the third peripheral electrode unit 125 of thesecond electrode 120 and a voltage VD applied to a region of the firstelectrode 110 corresponding to the third peripheral electrode unit 125of the second electrode 120 is defined as ΔV4D.

In one embodiment, the voltage differences ΔV1A, ΔV2B, ΔV3C, and ΔV4Dare controlled to be substantially equal to each other. In anotherembodiment, the voltage differences ΔV1A, ΔV2B, ΔV3C, and ΔV4D arecontrolled such that difference between two among the voltagedifferences ΔV1A, ΔV2B, ΔV3C, and ΔV4D is smaller than a predeterminedvalue.

That is, as described above, since the voltages VA, VB, VC, and VDapplied to the first electrode 110 are sequentially increased, voltagesV1, V2, V3, and V4 applied to the regions of the second electrode 120are also controlled to be sequentially increased.

In an example of an organic light emitting device, when an organic lightemitting device is used as an illumination device, the area of a firstelectrode increases, and the voltage drop problem also increases.Therefore, it is not easy to secure a uniform brightness on an entireregion of the organic light emitting device. Also, in order to addressthe voltage drop problem, an auxiliary electrode is additionally formedon the first electrode. However, problems of process complexity, processfailure, increase in costs, and increase in the process time occur aswell.

However, in the organic light emitting device 100, according toembodiments of the present invention, although a voltage drop occurs inthe first electrode 110, since different voltages are respectivelyapplied to the central electrode unit 121 of the second electrode 120,the first peripheral electrode unit 123, the second peripheral electrodeunit 124, and the third peripheral electrode unit 125, a uniform voltagedrop between the first electrode 110 and the second electrode 120 can bemaintained over the entire region of the organic light emitting device100.

Through the above method, it is possible to secure a uniform brightnessover the entire region of the organic light emitting device 100. As aresult, it is possible to readily manufacture an illumination devicehaving a high brightness characteristic.

Also, in the current embodiment, the recessed portion 110 a is formed tocorrespond to the second electrode voltage application structure 130.That is, different voltages are respectively applied to the centralelectrode unit voltage application unit 131, the first peripheralelectrode voltage application unit 133, the second peripheral electrodevoltage application unit 134, and the third peripheral electrode voltageapplication unit 135, and thus, an abnormal light emission phenomenonoccurs at a position corresponding to the second electrode voltageapplication structure 130. However, in the current embodiment, a voltageis not applied to the recessed portion 110 a through the first electrode110 since the recessed portion 110 a is formed in the first electrode110. Therefore, light emission does not occur from the intermediatelayer 140, and as a result, an abnormal light emission is fundamentallyblocked.

FIGS. 7 and 8 are graphs showing voltages applied to the first electrode110 and the second electrode 120 by using the power unit 160. Thevoltages V1, V2, V3, and V4 are outputs from the second terminalstructure 167 of the power unit 160, and the voltage VE is an outputfrom the first terminal unit 165 of the power unit 160.

Referring to FIG. 7, the first terminal unit 165 and the second terminalstructure 167 of the power unit 160 output the voltages V1, V2, V3, V4,and VE. More specifically, the power unit 160 may output the voltage VEin the first terminal unit 165 and apply the voltage VE to the firstelectrode 110. The voltage VE may be, for example, 7V.

The power unit 160 outputs the voltage V1 in the central connectionterminal unit 161 and applies the voltage V1 to the central electrodeunit 121 of the second electrode 120. The voltage V1 may be, forexample, −3V. The power unit 160 outputs the voltage V2 in the firstperipheral electrode connection terminal unit 162 and applies thevoltage V2 to the first peripheral electrode unit 123 of the secondelectrode 120. The voltage V2 may be, for example, −2V. The power unit160 outputs the voltage V3 in the second peripheral electrode connectionterminal unit 163 and applies the voltage V3 to the second peripheralelectrode unit 124 of the second electrode 120. The voltage V3 may be,for example, −1V. The power unit 160 outputs the voltage V4 in the thirdperipheral electrode connection terminal unit 164 and applies thevoltage V4 to the third peripheral electrode unit 125 of the secondelectrode 120. The voltage V4 may be, for example, 0V.

As described above, the power unit 160 may apply the voltages V1, V2,V3, V4, and VE to the second electrode 120 and the first electrode 110simultaneously. Although a voltage drop may occur in the first electrode110, since the differential voltages V1, V2, V3, V4, and VE are appliedto the second electrode 120, the organic light emitting device 100 cansecure uniform brightness throughout the regions thereof.

Referring to FIG. 8, the power unit 160 may apply the voltages V1, V2,V3, V4, and VE to the second electrode 120 differentially and on adifferent time basis. In more detail, in some embodiments, the powerunit 160 applies the voltage V1 to the central electrode unit 121corresponding to the center of the first electrode 110 where the voltagedrop occurs most for a longer period of time than the voltages V2, V3,and V4 applied to the peripheral electrode unit 122, applies the voltageV2 to the first peripheral electrode unit 123 for a shorter period oftime than the voltage V1, applies the voltage V3 to the secondperipheral electrode unit 124 for a shorter period of time than thevoltage V2, and applies the voltage V4 to the third peripheral electrodeunit 125 for a shorter period of time than the voltage V3. As such,periods of time taken to apply the voltages V1, V2, V3, and V4 aredifferentially controlled, thereby securing more uniform brightness ofthe organic light emitting device 100.

FIG. 9 is a schematic plan view of an organic light emitting device 200according to another embodiment of the present invention. Forconvenience of explanation, differences from the previous embodimentwill be mainly described.

The organic light emitting device 200 includes a substrate 201, a firstelectrode (not shown), an intermediate layer (not shown), a secondelectrode 220, and the power unit 160. The second electrode 220 includesa central electrode unit 221 and a peripheral electrode unit 222. Theperipheral electrode unit 222 includes a first peripheral electrode unit223, a second peripheral electrode unit 224, and a third peripheralelectrode unit 225. However, the present invention is not limitedthereto, that is, organic light emitting device 200 may include one ormore than three peripheral electrode units 222.

Four electrode voltage application units 211 are connected to the firstelectrode (not shown) to apply a voltage to the first electrode (notshown). The electrode voltage application units 211 are electricallyconnected to the first terminal unit 165 of the power unit 160 viaelectric wires. Although one of the electrode voltage application units211 and the first terminal unit 165 are connected to each other in FIG.9, the four electrode voltage application units 111 are connected toside surfaces of the first terminal unit 165. The power unit 160 appliesan identical voltage to the four electrode voltage application units211.

The second electrode voltage application structure 230 is connected tothe second electrode 220 to apply a voltage to the second electrode 220.The second electrode voltage application structure 230 includes acentral electrode unit voltage application unit 231, a first peripheralelectrode voltage application unit 233, and a second peripheralelectrode voltage application unit 234, and a third peripheral electrodevoltage application unit 235.

The second electrode voltage application structure 230 is connected tothe second terminal structure 167 of the power unit 160. That is, thecentral electrode unit voltage application unit 231 is electricallyconnected to the central connection terminal unit 161, the firstperipheral electrode voltage application unit 233 is electricallyconnected to the first peripheral electrode connection terminal unit162, the second peripheral electrode voltage application unit 234 iselectrically connected to the second peripheral electrode connectionterminal unit 163, and the third peripheral electrode voltageapplication unit 235 is electrically connected to the third peripheralelectrode connection terminal unit 164.

Edges of the central electrode unit 221 of the second electrode 220 havecurved lines. Also, edges of the first peripheral electrode unit 223have curved lines.

When a voltage is applied to the first electrode (not shown) through theelectrode voltage application units 211, as described above, a voltagedrop strongly occurs in each region of the first electrode formed as onebody. That is, the values of voltages applied towards the center P fromregions adjacent to the electrode voltage application units 211 of thefirst electrode are gradually reduced. Also, at this time, due to thevoltage drop, boundary lines between the regions of the first electrodewhere the voltage is different may be curved. That is, a boundary linebetween the central electrode unit 221 of the second electrode 220 andthe first peripheral electrode unit 223 may be formed as a curved lineto effectively reflect the voltage drop of the first electrode.

However, the current embodiment is not limited thereto, that is, asingle boundary line between the central electrode unit 221 and thefirst peripheral electrode unit 223 may be formed as a curved line.Also, boundary lines of the second peripheral electrode unit 224 mayalso be formed as curved lines.

The organic light emitting device according to embodiments of thepresent invention can readily secure a uniform brightness characteristicand enhance light-emitting efficiency.

While embodiments of the present invention have been particularly shownand described, it will be understood by those of ordinary skill in theart that various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present invention as definedby the following claims.

1. An organic light emitting device comprising: a first electrode formedover a substrate; an intermediate layer that is formed over the firstelectrode and comprises an organic light emitting layer; a secondelectrode that comprises a central electrode unit disposed in a centralregion and a peripheral electrode unit separated from the centralelectrode unit and disposed in a peripheral region, wherein theintermediate layer is disposed between the first and second electrodes;and a power unit configured to apply voltages to the first electrode andthe second electrode, wherein the power unit is configured to applydifferent voltages to the first electrode, the central electrode unit,and the peripheral electrode unit.
 2. The organic light emitting deviceof claim 1, wherein the power unit is configured to individually controlthe voltages applied to the central electrode unit and the peripheralelectrode unit and is further configured to apply different voltages tothe central electrode unit and the peripheral electrode unit.
 3. Theorganic light emitting device of claim 1, wherein the power unitconfigured to apply the voltage to the peripheral electrode unit beforeapplying the voltage to the central electrode unit.
 4. The organic lightemitting device of claim 1, wherein the first electrode is formed as asingle body.
 5. The organic light emitting device of claim 1, whereinthe first electrode is connected to electrode voltage application unitsand a voltage is applied to edges of the first electrode.
 6. The organiclight emitting device of claim 5, wherein the electrode voltageapplication units are formed on the edges of the first electrode,respectively.
 7. The organic light emitting device of claim 1, whereinthe power unit is connected to the electrode voltage application unitsand configured to apply the voltage to the first electrode.
 8. Theorganic light emitting device of claim 1, wherein the central electrodeunit comprises at least an edge which comprises a curved portion.
 9. Theorganic light emitting device of claim 1, wherein the center of thefirst electrode coincides with the center of the central electrode unit.10. The organic light emitting device of claim 1, wherein the center ofthe central electrode unit coincides with the center of the peripheralelectrode unit.
 11. The organic light emitting device of claim 1,further comprising electrode voltage application units formed to applyvoltages to the second electrode, wherein the first electrode comprisesa recess portion recessed from an edge of the first electrode, and therecess portion is formed to overlap the electrode voltage applicationunits.
 12. The organic light emitting device of claim 1, wherein thesecond electrode further comprises at least an additional peripheralelectrode unit separated from the peripheral unit, wherein theperipheral electrode unit is disposed to surround the central electrodeunit, and wherein the at least an additional peripheral electrode unitis disposed to surround the peripheral electrode unit disposed tosurround the central electrode unit.
 13. The organic light emittingdevice of claim 12, wherein the power unit is connected to the electrodeunits and configured to individually apply voltages to the electrodeunits.
 14. The organic light emitting device of claim 12, wherein afirst one of the electrode units is disposed farther from the center ofthe second electrode than a second one of the electrode units, and thevoltage applied to the first electrode unit is higher than that appliedto the second electrode unit.
 15. The organic light emitting device ofclaim 12, wherein the power unit is configured to differentially controlperiods of time of application of the voltages to the electrode units.16. The organic light emitting device of claim 12, wherein the powerunit configured to apply the voltage to the central electrode unit for alonger period of time than the peripheral electrode unit.
 17. Theorganic light emitting device of claim 12, wherein a first one of theelectrode units is disposed closer to the center of the second electrodethan a second one of the electrode units, and the period of time ofapplication of the voltage to the first electrode unit is longer thanthat of the second electrode unit.
 18. The organic light emitting deviceof claim 12, wherein the centers of the electrode units are formed tocoincide with each other.
 19. The organic light emitting device of claim12, wherein edges of at least some of the electrode units comprisecurved portions.